In motor vehicles such as minivans, sport utility vehicles and the like, it has become common practice to provide the vehicle body with a large rear opening. A liftgate (also referred to as a tailgate) is typically mounted to the vehicle body with hinges for pivotal movement about a transversely extending axis between an open position and a closed position. The liftgate is operated either manually or electronically via a power drive mechanism including a reversible electric motor. For example, such arrangements are shown in commonly assigned U.S. Pat. Nos. 5,531,498; 5,563,483; and 5,448,856.
There are instances, however, when it is desirable to disable the power drive mechanism associated with the liftgate. For example, during power operation of a vehicle liftgate, the liftgate may unexpectedly encounter an obstacle in its path. It is therefore desirable to cease its powered movement in that event to prevent damage to the obstacle and/or the liftgate and its power drive mechanism. U.S. Pat. No. 6,297,605 discloses a powered liftgate system having a pinch sensor for causing the liftgate movement to stop upon sensing an encounter with an obstacle.
An electronic liftgate system also requires a full open switch in order to maintain a controlled opening and closing in situations where the liftgate was left open and an associated controller was put to sleep due to vehicle energy conservation. When the liftgate is closed, the closed position is known even after the controller goes to sleep since a latch switch is activated. However, when the liftgate is left open and the controller is put to sleep, the position memory is lost and the controller only knows that it is not in a closed position. This is important because when the position is known, the controller can slow down the operation of the liftgate just before full open and close to prevent the system from opening or closing too fast. In current systems, when the position memory has been lost, the liftgate is controlled to go to the full open position via a full open switch, identified by reference numeral 11 in FIG. 3. The switch 11 is mechanically activated just before full open position and triggers the controller to start its slow down for a controlled full open position.
Although full open switches and pinch sensors are available separately to identify full open position and to disable movement of the liftgate under pinch conditions, respectively, these components are typically packaged separately within the vehicle with an expense associated with each component. It is, thus, desirable to use the pinch sensor for sensing obstructions and providing indication of a full open position in a cost effective manner.